Electronic equipment often employs printed circuit boards or cards. These cards typically are mounted in a chassis or card rack by stacking the cards in row alignment with one another. Row alignment in the chassis is defined by slotted or spaced surfaces within or on the chassis, with each circuit board placed in a slot or between a pair of spaced surfaces. A retainer may be provided in the chassis slot to captivate a card positioned therein. Many applications for such retainers require high performance that will captivate a printed circuit board under the most extreme shock and vibration conditions such as those encountered by spacecraft or military aircraft.
Exemplary printed circuit board retainers include a cam-type retainer such as that described in U.S. Pat. No. 3,970,198 and a multi-wedge type retainer such as that described in U.S. Pat. Nos. 4,823,951 and 5,036,428, the contents of which patents are incorporated herein by reference. The multi-wedge type retainers include a partially threaded screw or rod upon which are mounted a plurality of slideable members in an end-to-end relationship. The members disposed on the rod have wedge-shaped end portions which engage one another and serve to move at least one of the members in a transverse direction relative to the rod when the members are moved towards one another along the rod. Such movement may be achieved by providing the rod with screw threads to engage and move the distal-most member when the rod is rotated. Alternatively, the movement may result from the action of a lever assembly used to draw the rod away from the distal-most member, thereby pulling that member toward its companions.
Commonly, the rod in prior art retainers is threaded at one end to engage with mating threads on a nut attached to the end-most sliding member mounted on the rod. The opposite end of the rod includes a portion that may be engaged by a tool to allow the rod to be rotated. In so doing, the members are moved toward one another as the threaded rod is rotated in the tightening direction.
The transverse direction in which the member is moved acts to engage a clamping surface of that member against an edge of the printed circuit board. The opposite edge of the board is thereby forced into contact with, and clamped against, a spaced surface fixedly connected to or integral with the chassis in which the board is to be mounted. Typically, the spaced surface fixedly connected to the chassis is the wall of a housing that is screwed or rivetted to the chassis.
The housings of the prior art are mounted (e.g., rivetted or screwed) to the chassis during the manufacture process, or more commonly, by the end user during the application. If the housing is to be mounted by the end user, the retainers and housings are normally shipped unassembled, although these components can be shipped assembled with instructions to disassemble and remove the retainer from the housing before mounting the housing to the chassis. Disassembly is required because the retainer rod cannot be withdrawn from the housing without removing the slideable members. Following attachment of the housing to the chassis, the end user must re-assemble the retainer in the housing by inserting a first end of the retainer rod through an opening in a housing endwall, positioning the slideably mounted members on the rod, screwing the first rod end into a nut attached to the end-most sliding member mounted on the rod, and passing the first rod end through a second housing endwall opening.
In view of the above, a need exists for a retainer assembly which eliminates or substantially reduces the labor-intensive, time-consuming process for mounting a retainer assembly to a chassis, particularly for field installation by an end user. The improved assembly should be capable of receiving and retaining a fully assembled circuit board retainer and should permit initial installation, replacement, repair and/or inspection of the retainer without requiring retainer disassembly.